[Ted Fletcher]

Hi Jake, yes, I have the circuit diagrams for the 1228; it’s a delightful simple mixer, it sounds good and there really hasn’t been very much better in the years since then.
I will be sending the circuit diagrams by email direct to you.
‘B-check’ is just a simple switched function in the monitor section so that should be no problem.
As for cleaning, use WD40 or one of the artificial greases…. don’t use switch cleaner or the pots might easily fall apart!
I can’t help with the lamps; I would suggest altering it to take white LEDs.
The monitor pots were always the ones that disintegrated on these mixers.
All the best with the project…… it’s surprising how many of these old mixers are still around…… like me really.

[Ted Fletcher]

Hi Yan, thanks for your post.
I’m afraid that your VC6 has a serious power supply problem. I’m afraid I don’t have the circuit diagram for the VC6, but it is very similar to the VC3 and if you would like to drop me an email at [email protected] I will email you a copy of this…. But I would suggest that the fix is not simple. Once the power supply fails on these units, it’s often the case that it takes out most of the integrated circuits, so the fix could be expensive.
I have an arrangement where I service all old equipment of my design, for a fixed fee of £25 plus the cost of returning it.
I can’t guarantee to fix this one, but if you like I will try.

[Ted Fletcher]

Thanks for the post Koen, I have answered directly by email; it sounds like an integrated circuit slightly out of spec causing an offset voltage. I have suggested a fix in my email.

[Ted Fletcher]

Hello Ed, This is delving back a good many years! The AM and ACM modules all ran on 15-0-15 rails and these appeared on pins 13 and 15 of the edge connector, but there the memory fails. Usually audio ground was on pin 24… but don’t bank on that one. I’m afraid I don’t have any circuit details from those days, but the mic amps were conventional transformer input using mostly Sowter transformers. In the mixers we used quite simple EQ; variations on Baxendall HF and LF with sometimes a simple tuned mid.
Send me a picture of the modules and it might well jog more memories!

[Ted Fletcher]

The output level from the mic amps is intentionally low compared to the main outputs, this is so that a suitable overload margin is retained. To use the direct outputs, the record inputs should be re-configured to a suitably lower level, around 26dB below clip, and should be ‘bridging’ inputs; that is, NOT 600 ohm..
The main outputs (and the monitor outputs) are designed to operate at zero level with a clip level at about +25dBu. If you are getting apparent low level on the main outputs, I would suggest that the connections are not correct…. this is an electronic floating output and if the ‘pin 3’ or ‘ring’ of the jack is not connected then the output will look very low indeed.

I have posted this as it might be useful to other users of the M16…… I know that a number of studios use them as stereo sub-mixes for drums…. and to get that transparrent sound, the overload margin is all important!

[Ted Fletcher]

The standard 828 was unbalanced out. We did make one or two specials with balanced out, but the vast majority would be unbalanced.
There seems to be a big market for these nowadays. Perhaps we should make a 21st century version! 😯

[Ted Fletcher]

We don’t have any distribution deals in USA or Canada…… I find that with communications being so good, we can service users from the UK…. after all, it’s closer from Torquay to Toronto than it is from Toronto to Vancouver!
But I don’t have any VC2s!
But I can do you a good deal on a P110 or a P10.

[Ted Fletcher]

This is a brief history of the mic amps in JM equipment…
The first mic amp was the VC1 ‘Brick’. This circuit was a conventional transformer into a multi-stage integrated circuit amplifier. This gave a very low noise and low distortion amp, very suitable for recording and broadcasting.
The same amplifier was used in the early VC1 2U rack units.
In 1999 I introduced a new transformerless amplifier in the VC1 (called the VC1QCS) this was actually very slightly more noisy than the earlier type, but had a couple of huge advantages…. it was almost impossible to overload, and it works very well with very long mic cables. In addition, the distortion is very low and does not increase at low frequencies like the transformer.
The VC2 was a special low-gain mic amp using a transformer, but the main gain section was a valve (vacuum tube).
The circuit of the VC1QCS was taken over to the ‘VC Twin’, and became the standard mic-amp circuit; it proved to be extremely rugged and versatile.
I designed a new version of it for the VC3, with a better ‘feel’ to the mic gain control and this same circuit was used in the VC6.
The mic transformers used were all made by ‘OEP’ in the UK and were of a type normally used for line level circuits… I configured the circuitry so that the noise, distortion and overload margins were all optimised.

To complete the picture, I need to mention the present generation of mic amps used in TFPRO gear….. These are all transformer based, but with circuitry that eliminates overload…. present mic amps will easily take +26dB at all frequencies!
In terms of quality and ‘sound’, there is no doubt that the early ‘Brick’ was very good, but I think it is equalled by the P110.

[Ted Fletcher]

Will, I have sent the circuit diagrams to your email address.

[Ted Fletcher]

I have emailed the cct detail.
BTW, I’m happy to let users see circuit details of any of the older gear (and even the newer stuff) as long as it is for a legitimate reason.

[Ted Fletcher]

I have a red face on this one! There is a mistake on the circuit diagram…. I’m fixing it!

[Ted Fletcher]

Just for once I think I may have an answer for you… I think the problem could be in the jack socket on the front panel of the P1. I have had a P1 in the past where there was dirt on the contacts of the jack socket, and this affected the mic input. Try plugging and unplugging a jack into that socket…… it might well fix it!
If the problem continues, consider sending it back to me to have a look at.

[Ted Fletcher]

Email me direct ([email protected]) with your address and I will gladly send you a replacement transformer.
The P1200 is a specialist comms transformer normally used in telephone systems. In the P38 I use it in a very novel way in a circuit that increases its frequency response and eliminates distortion. I don’t recommend using any other transformer.

[Ted Fletcher]

I’m afraid that’s not enough info to let me diagnose the hum and noise……The P10 is a piece of high gain gear and it would be very easy to mis-use it and get some nasty results….. pls email me direct on [email protected].
Thanks

[Ted Fletcher]

I’ve got a policy here, that I will fix any old gear of my design for a fixed fee of £25 plus the cost of returning it.
This is stretching it a bit!! But what the heck…. I can’t promise to replace the meter glass although I will have a look around….. and I don’t have any stock of the faders, but I can get it back working properly again…. I would seriously avoid any modifications, in terms of performance these mixers stood up well…. it will be interesting to hang a spectrum analyser on it!

Yes, when You get it, let me have it by all means (I’m assuming you are in the UK) and I will fix whatever it needs.
(If you are in the USA… and this goes for anyone sending equipment, we have had recent problems with customs on equipment sent back for servicing; it’s not impossible, but there are delays.)

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